Fluid pumping capillary seal for a fluid dynamic bearing

ABSTRACT

An apparatus is provided including a shaft, wherein the shaft is stationary. A rotatable component is configured to rotate with respect to the shaft. A fluid is operable to flow between the shaft and the rotatable component. A limiter is at a first axial end of the shaft, and a cup is at a second axial end of the shaft. An axially extending grooved region is between the limiter and the rotatable component.

RELATED APPLICATIONS

This application is a continuation of prior application Ser. No.14/033,215, filed on Sep. 20, 2013, which is a continuation of priorapplication Ser. No. 12/328,710, filed on Dec. 4, 2008.

BACKGROUND

Disc drive memory systems store digital information that is recorded onconcentric tracks on a magnetic disc medium. At least one disc isrotatably mounted on a spindle, and the information, which can be storedin the form of magnetic transitions within the discs, is accessed usingread/write heads or transducers. A drive controller is typically usedfor controlling the disc drive system based on commands received from ahost system. The drive controller controls the disc drive to store andretrieve information from the magnetic discs. The read/write heads arelocated on a pivoting arm that moves radially over the surface of thedisc. The discs are rotated at high speeds during operation using anelectric motor located inside a hub or below the discs. Magnets on thehub interact with a stator to cause rotation of the hub relative to thestator. One type of motor has a spindle mounted by means of a bearingsystem to a motor shaft disposed in the center of the hub. The bearingspermit rotational movement between the shaft and the sleeve, whilemaintaining alignment of the spindle to the shaft.

Disc drive memory systems are being utilized in progressively moreenvironments besides traditional stationary computing environments.Recently, these memory systems are incorporated into devices that areoperated in mobile environments including digital cameras, digital videocameras, video game consoles and personal music players, in addition toportable computers. These mobile devices are frequently subjected tovarious magnitudes of mechanical shock as a result of handling. As such,performance and design needs have intensified including improvedresistance to shock events including axial and angular shock resistance,vibration response, and improved robustness.

The read/write heads must be accurately aligned with the storage trackson the disc to ensure the proper reading and writing of information.Moreover, a demand exists for increased storage capacity and smallerdisc drives, which has led to the design of higher recording arealdensity such that the read/write heads are placed increasingly closer tothe disc surface. Precise alignment of the heads with the storage tracksis needed to allow discs to be designed with greater track densities,thereby allowing smaller discs and/or increasing the storage capacity ofthe discs. Because rotational accuracy is critical, many disc drivespresently utilize a spindle motor having a fluid dynamic bearing (FDB)situated between a shaft and sleeve to support a hub and the disc forrotation. The stiffness of the fluid dynamic bearing is critical so thatthe rotating load is accurately and stably supported on the spindlewithout wobble or tilt. In a hydrodynamic bearing, a lubricating fluidis provided between a fixed member bearing surface and a rotating memberbearing surface of the disc drive. Hydrodynamic bearings, however,suffer from sensitivity to external loads or mechanical shock.

A method of providing a compact fluid sealing system is to employasymmetric sealing. Many bearings utilize an asymmetric fluid sealingsystem with a capillary seal situated on one end of the bearing, and agrooved pumping seal on an opposite bearing end. However, in thesesealing systems, a problem arises known as jog, jog being the rapid andrepeated opening and closing of axial spaces between relativelyrotatable components that can dispel oil from, or draw air into, thesespaces. In contemporary designs, unless the flow resistance of arecirculation channel is sufficiently low, oil will either be expelledfrom the fluid seals during compression, or air will be drawn into thefluid seals during expansion.

Further, a sufficient amount of lubricant such as oil must be maintainedin a capillary seal reservoir to offset losses. If a shock event occurswith a motor having an insufficient volume of lubricant, rotatingsurfaces may come in direct contact with stationary components. The drysurface-to-surface contact may lead to particle generation or gallingand lock-up of the motor during contact. Particle generation andcontamination of the bearing fluid may also result in reducedperformance or failure of the spindle motor or disc drive components.

SUMMARY

An apparatus is provided including a shaft, wherein the shaft isstationary. A rotatable component is configured to rotate with respectto the shaft. A fluid is operable to flow between the shaft and therotatable component. A limiter is at a first axial end of the shaft, anda cup is at a second axial end of the shaft. An axially extendinggrooved region is between the limiter and the rotatable component. Theseand various other features and advantages will be apparent from areading of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated by reference to thefollowing detailed description, when taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a top plan view of a disc drive data storage system in whichthe present invention is useful, in accordance with an embodiment of thepresent invention;

FIG. 2 is a sectional side view of a contemporary spindle motor used ina disc drive data storage system incorporating a contemporary fluidsealing system;

FIG. 3 is a perspective view of a cross section of a portion of a fluiddynamic bearing motor, illustrating a pumping capillary sealing systemin the form of a retainer, in accordance with an embodiment of thepresent invention;

FIG. 4 is an enlarged perspective view of a pumping capillary sealingsystem in the form of a retainer, as in FIG. 3, in accordance with anembodiment of the present invention;

FIG. 5 is a perspective view of a cross section of a portion of a fluiddynamic bearing motor, illustrating a pumping capillary sealing systemin the form of a cup, in accordance with another embodiment of thepresent invention;

FIG. 6 is an enlarged perspective view of a pumping capillary sealingsystem in the form of a cup, as in FIG. 5, in accordance with anembodiment of the present invention;

FIG. 7 is a representative view showing oil volume from a pumpingcapillary seal groove or slot, as in FIG. 4 or FIG. 6, in accordancewith an embodiment of the present invention;

FIG. 8 is an enlarged perspective view of a pumping capillary sealingsystem in the form of a retainer, as in FIG. 3, and further comprisingsweeping ribs and a plenum region, in accordance with an embodiment ofthe present invention;

FIG. 9 is an enlarged perspective view of a pumping capillary sealingsystem in the form of a cup, as in FIG. 5, and further comprisingsweeping ribs and a plenum region, in accordance with an embodiment ofthe present invention; and

FIG. 10 is a sectional side view of a portion of a fluid dynamic bearingmotor having a conical component, illustrating a pumping capillarysealing system, in accordance with another embodiment of the presentinvention.

DETAILED DESCRIPTION

Exemplary embodiments are described with reference to specificconfigurations. Those of ordinary skill in the art will appreciate thatvarious changes and modifications can be made while remaining within thescope of the appended claims. Additionally, well-known elements,devices, components, methods, process steps and the like may not be setforth in detail in order to avoid obscuring the invention.

An apparatus and method are described herein for providing a compact,robust, and power efficient fluid sealing system with fluid pumping andcapillary features, for a fluid dynamic bearing. The present inventionprovides improved shock resistance and vibration response, and therebyincreases reliability and performance of a disc drive memory system.Concerns of motor jog are addressed, jog being the rapid and repeatedopening and closing of axial spaces between relatively rotatablecomponents that can dispel oil from, or draw air into, these spaces. Thepresent invention is especially useful with small form factor discdrives having constraints in motor height, such as a 2.5 inch discdrive, requiring high performance including high rotational speed andlarge areal density.

It will be apparent that features of the discussion and claims may beutilized with disc drive memory systems, low profile disc drive memorysystems, spindle motors, brushless DC motors, various fluid dynamicbearing designs including hydrodynamic and hydrostatic bearings, andother motors employing a stationary and a rotatable component, includingmotors employing conical bearings. Further, embodiments of the presentinvention may be employed with a fixed shaft or a rotating shaft. Also,as used herein, the terms “axially” or “axial direction” refers to adirection along a centerline axis length of the shaft (i.e., along axis260 of shaft 202 shown in FIG. 2), and “radially” or “radial direction”refers to a direction perpendicular to the centerline axis 260, andpassing through centerline axis 260. Also, as used herein, theexpressions indicating orientation such as “upper”, “lower”, “top”,“bottom”, “height” and the like, are applied in a sense related tonormal viewing of the figures rather than in any sense of orientationduring particular operation, etc. These orientation labels are providedsimply to facilitate and aid understanding of the figures as describedin this Description and should not be construed as limiting.

Referring to the drawings wherein identical reference numerals denotethe same elements throughout the various views, FIG. 1 illustrates a topplan view of a typical disc drive data storage system 110 in which thepresent invention is useful. Features of the discussion and claims arenot limited to this particular design, which is shown only for purposesof the example. Disc drive 110 includes base plate 112 that is combinedwith cover 114 forming a sealed environment to protect the internalcomponents from contamination by elements outside the sealedenvironment. Disc drive 110 further includes disc pack 116, which ismounted for rotation on a spindle motor (described in FIG. 2) by discclamp 118. Disc pack 116 includes a plurality of individual discs, whichare mounted for co-rotation about a central axis. Each disc surface hasan associated head 120 (read head and write head), which is mounted todisc drive 110 for communicating with the disc surface. In the exampleshown in FIG. 1, heads 120 are supported by flexures 122, which are inturn attached to head mounting arms 124 of actuator body 126. Theactuator shown in FIG. 1 is a rotary moving coil actuator and includes avoice coil motor, shown generally at 128. Voice coil motor 128 rotatesactuator body 126 with its attached heads 120 about pivot shaft 130 toposition heads 120 over a desired data track along arc path 132. Thisallows heads 120 to read and write magnetically encoded information onthe surfaces of discs 116 at selected locations.

A flex assembly provides the requisite electrical connection paths forthe actuator assembly while allowing pivotal movement of the actuatorbody 126 during operation. The flex assembly (not shown) terminates at aflex bracket for communication to a printed circuit board mounted to thebottom side of disc drive 110 to which head wires are connected; thehead wires being routed along the actuator arms 124 and the flexures 122to the heads 120. The printed circuit board typically includes circuitryfor controlling the write currents applied to the heads 120 during awrite operation and a preamplifier for amplifying read signals generatedby the heads 120 during a read operation.

Referring to FIG. 2, a sectional side view is illustrated of acontemporary spindle motor as used in a disc drive data storage system110. This fluid dynamic bearing motor includes a rotatable componentthat is relatively rotatable about a stationary component, defining ajournal bearing 206 therebetween. In this example, the rotatablecomponents include shaft 202 and hub 210. In an alternative design, theshaft 202 is a stationary component, and the sleeve 204 is a rotatablecomponent. Hub 210 includes a disc flange, which supports disc pack 116(shown in FIG. 1) for rotation about axis 260 of shaft 202. Shaft 202and hub 210 are integral with backiron 215. One or more magnets 216 areattached to a periphery of backiron 215. The magnets 216 interact with alamination stack 214 attached to the base 220 to cause the hub 210 torotate. Magnet 216 can be formed as a unitary, annular ring or can beformed of a plurality of individual magnets that are spaced about theperiphery of hub 210. Magnet 216 is magnetized to form two or moremagnetic poles. The stationary components include sleeve 204 and stator211, which are affixed to base plate 220. Bearing 206 is establishedbetween the sleeve 204 and the rotating shaft 202. A thrust bearing 207is established between hub 210 and sleeve 204. Thrust bearing 207provides an upward force on hub 210 to counterbalance the downwardforces including the weight of hub 210, axial forces between magnet 216and base plate 220, and axial forces between stator lamination stack 214and magnet 216. In the case of a fluid dynamic bearing spindle motor, afluid, such as lubricating oil fills the interfacial regions betweenshaft 202 and sleeve 204, and between hub 210 and sleeve 204, as well asbetween other stationary and rotatable components. While the presentfigure is described herein with a lubricating fluid, those skilled inthe art will appreciate that useable fluids include a liquid, a gas, ora combination of a liquid and gas.

FIG. 3 is a perspective view of a cross section of a portion of a fluiddynamic bearing motor, illustrating a fluid pumping capillary sealingsystem 310 in the form of a retainer (referred to as PCS retainer 310),in accordance with an embodiment of the present invention. A bearing 318containing fluid is defined between facing surfaces of shaft 302 andsleeve 304. PCS retainer 310 is positioned at an end of the bearing, forsealing the fluid within the motor. In the example shown, a capillarysealing component 320 having a fluid reservoir 322 is positioned at anaxially opposite end of the motor. In an alternative embodiment, asecond pumping capillary sealing system is utilized at the axiallyopposite end of the motor from the pumping capillary sealing system 310.It is to be appreciated that other fluid seals or designs may beutilized at the axially opposite end from the fluid pumping capillarysealing system 310. Further, the present invention may be designed as,or utilized with, either an asymmetric sealing system or a symmetricsealing system.

Together, the pumping capillary sealing system 310 and the capillarysealing component 320 provide an asymmetric sealing system. The pumpingcapillary seal acts as a stiffer, lower volume seal, while the capillaryseal acts as a softer, higher volume seal. Stiff and soft refer to thetendency of the respective seals to push fluid into the contained volumeof the motor, which is a measure of the ratio of pressure change tovolume change. When the motor transitions from stationary to a spinningcondition, the pumping capillary sealing system 310 pumps fluid into thecapillary seal. Inexact balancing of the two seals can thus be allowed.The pumping capillary sealing system 310 pumps fluid toward thecapillary seal until the pumping capillary seal reduces to a fluidvolume to reach an equilibrium pressure with the capillary seal. Thatis, the pressure capability of the pumping capillary seal decreases asit looses fluid volume at a faster rate than the corresponding increasein pressure capability (with increasing fluid volume) of the capillaryseal. The fluid is thereby contained within the motor. In an embodiment,the area within the pumping capillary seal that was previously occupiedby fluid is replaced by air, by way of vent holes (described below).

In the example embodiment illustrated, the stationary shaft 302 isaffixed to the pumping capillary sealing system 310, as well as to thecapillary sealing component 320. The shaft 302 may further be affixed toa top cover (TCA) for added motor stability. Rotatable hub 308 andsleeve 304 rotate about a centerline axis of shaft 302. There is atradeoff of motor stiffness when designing motors with axial spacesavings. The present invention address this concern and providesimproved stiffness, resulting in the read/write heads of a storagedevice being accurately aligned with storage tracks on a disc, when thedevice is subjected to vibration. This allows discs to be designed withincreased track densities, and also allows for smaller discs and/orincreased storage capacity of discs. In particular, the stiffness of thefluid dynamic bearing is critical so that the rotating load isaccurately and stably supported on the spindle without wobble or tilt.

The pumping capillary seal is fluidly connected to the capillary seal byway of a fluid recirculation passageway 306 formed through the sleeve304. Contemporary motor design concerns of dry surface-to-surfacecontact, because of loss of lubricating fluid and the flow resistance ofa recirculation channel, are minimized because of the present inventionfluid pumping capillary sealing system.

In an embodiment, the fluid pumping capillary sealing system 310 is alsoformed as a limiter, the limiter affixed to the rotatable component. Thelimiter is employed for limiting axial displacement of the rotatablecomponents with respect to the stationary components. The radiallyextending surface 346 (FIG. 4) of the PCS retainer 310 also provides afluid containing surface, addressing concerns of dry surface-to-surfacecontact with the facing relatively rotatable surface.

Referring to FIG. 4, an enlarged perspective view is illustrated of apumping capillary sealing system in the form of a retainer (PCS retainer310), as in FIG. 3, in accordance with an embodiment of the presentinvention. The PCS retainer 310 has a radially extending surface 346 andan axially extending surface 348, with reference to a centerline axislength of the shaft (i.e., along axis 260 of shaft 202 shown in FIG. 2).The radially extending surface 346 extends from inner diameter (ID) 342to outer diameter (OD) 344. Radially extending surface 346 and axiallyextending surface 348 join at a junction of OD 344. Alternatively,surfaces 346 and 348 may extend at an angle rather than substantiallyaxially or radially.

The pumping capillary sealing system includes slot portions 332 and ribportions 334 formed on the radially extending surface 346, for pumpingfluid toward the bearing. In an embodiment, these fluid pumping groovesextend up to an outer perimeter of surface 340, such that rib portionsand slot portions are absent from the inner diameter 342. Fluid thuscontinuously remains upon surface 340 adjacent to fluid bearing 318. Theslot portions 332 are axially tapered and/or radially tapered toincreasingly diverge with respect to distance from the bearing (from ID342), as further described in FIG. 7. These fluid pumping grooves may beshaped in a variety of forms, including a spiral shape or a herringboneshape.

The pumping capillary sealing system also includes a capillary seal. Theslot portions 332 diverges at least to an area such that a capillaryseal fluid meniscus extending from the tapered slot 332 can shiftradially with respect to the bearing, when the rotatable component isstationary with respect to the stationary component. It is to beappreciated that the fluid meniscus can also shift radially, withrespect to the bearing, when the motor is rotating. The slot portions332 thus provides for fluid containment when the motor is stationary.When the motor spins, the spiral pumping shape pumps the fluid in thecapillary seal toward the bearing. The varying depth of the slots 332provide for fluid storage and an air containment groove. In anembodiment, the air containment groove is vented to accommodate rapidchanges in fluid volume due to jog.

In the embodiment illustrated, axially extending surface 348 alsoincludes auxiliary pumping ribs 338. These auxiliary pumping ribs 338extend the pumping surface to a greater distance, which further ensuresfluid is retained within the motor. In an alternative embodiment,axially extending surface 348 is without pumping ribs.

Turning now to FIG. 5, a perspective view is shown of a cross section ofa portion of a fluid dynamic bearing motor, illustrating a pumpingcapillary seal in the form of a cup, in accordance with anotherembodiment of the present invention. A bearing 418 containing fluid isdefined between facing surfaces of shaft 402 and sleeve 404. PCS cup 410is positioned at an end of the bearing, for sealing the fluid within themotor. In the example shown, a capillary sealing component 420 having afluid reservoir 422 is positioned at an axially opposite end of themotor.

Together, the pumping capillary sealing system 410 and the capillarysealing component 420 provide an asymmetric sealing system. The pumpingcapillary seal acts as a stiffer, lower volume seal, while the capillaryseal acts as a softer, higher volume seal. Stiff and soft refer to thetendency of the respective seals to push fluid into the contained volumeof the motor, which is a measure of the ratio of pressure change tovolume change. When the motor transitions from stationary to a spinningcondition, the pumping capillary sealing system 410 pumps fluid into thecapillary seal. Inexact balancing of the two seals can thus be allowed.The pumping capillary sealing system 410 pumps fluid toward thecapillary seal, until the pumping capillary seal looses enough fluidvolume to reach an equilibrium pressure with the capillary seal. Thatis, the pressure capability of the pumping capillary seal decreases asit looses volume at a faster rate than the corresponding increase inpressure capability (with increasing fluid volume) of the capillaryseal. The fluid is thereby contained within the motor.

In the example embodiment illustrated, the stationary shaft 402 isaffixed to the pumping capillary sealing system 410, as well as to thecapillary sealing component 420. The shaft 402 may further be affixed toa top cover (TCA) for added stability. Rotatable hub 408 and sleeve 404rotate about a centerline axis of shaft 402.

The pumping capillary seal is fluidly connected to the capillary seal byway of a fluid recirculation passageway 406 formed through the sleeve404. Contemporary motor design concerns of dry surface-to-surfacecontact, because of loss of lubricating fluid and the flow resistance ofa recirculation channel, are minimized because of the present inventionfluid pumping capillary sealing system.

In an embodiment, the fluid pumping capillary sealing system 410 is alsoformed as a limiter, the limiter affixed to the rotatable component. Thelimiter is employed for limiting axial displacement of the rotatablecomponents with respect to the stationary components. The radiallyextending surface 446 (FIG. 6) of the PCS cup 410 also provides a fluidcontaining surface, addressing concerns of dry surface-to-surfacecontact with the facing relatively rotatable surface.

FIG. 6 illustrates an enlarged perspective view of a pumping capillarysealing system in the form of a cup (PCS cup 410), as in FIG. 5, inaccordance with an embodiment of the present invention. PCS cup 410 hasa radially extending surface 446 and an axially extending surface 448,with reference to a centerline axis length of the shaft (i.e., alongaxis 260 of shaft 202 shown in FIG. 2). The radially extending surface446 extends from inner diameter (ID) 442 to outer diameter (OD) 444.Radially extending surface 446 and axially extending surface 448 join ata junction of OD 444. Alternatively, surfaces 446 and 448 may extend atan angle rather than substantially axially or radially.

The pumping capillary sealing system includes slot portions 432 and ribportions 434 formed on the radially extending surface 446, for pumpingfluid toward the bearing. In an embodiment, these fluid pumping groovesextend to an outer perimeter of surface 440, wherein surface 440interfaces with shaft 402. The slot portions 432 are axially taperedand/or radially tapered to increasingly diverge with respect to distancefrom the bearing (from ID 442), as further described in FIG. 7. Thesefluid pumping grooves may be shaped in a variety of forms, including aspiral shape or a herringbone shape.

The pumping capillary sealing system also includes a capillary seal. Theslot portions 432 diverges at least to an area such that a capillaryseal fluid meniscus extending from the tapered slot 432 can shiftradially with respect to the bearing, when the rotatable component isstationary with respect to the stationary component. It is to beappreciated that the fluid meniscus can also shift radially, withrespect to the bearing, when the motor is rotating. The slot portions432 thus provides for fluid containment when the motor is stationary.When the motor spins, the spiral pumping shape pumps the fluid in thecapillary seal toward the bearing. The varying depth of the slots 432provide for fluid storage and an air containment groove. In anembodiment, the air containment groove is vented by vents 450 toaccommodate rapid changes in fluid volume due to jog.

In the embodiment illustrated, axially extending surface 448 alsoincludes auxiliary pumping ribs 438. These auxiliary pumping ribs 438extend the pumping surface to a greater distance, which further ensuresfluid is retained within the motor. In an alternative embodiment,axially extending surface 448 is without pumping ribs.

FIG. 7 is a representative view showing oil volume from a pumpingcapillary seal groove or slot, as in FIG. 4 or FIG. 6, in accordancewith an embodiment of the present invention. The oil volume shownrepresents the volume within slot portions 332 (FIG. 4). The innerdiameter (ID) 342 and the outer diameter (OD) 344 are indicated. Theslot portions 332 are axially tapered and/or radially tapered toincreasingly diverge with respect to distance from the bearing (from ID342). In an embodiment, these slot portions 332 are tapered in threedimensions. In an example embodiment, the slot portion 322 has an axialdepth in the range of up to 30 microns at inner diameter (ID) 342radially closest to the bearing, and 50 microns to 400 microns at outerdiameter (OD) 344 radially furthest from the bearing.

In the example embodiment as shown, the nominal total oil volume of theslot portion 332 is 0.59 mm³. The nominal fluid meniscus height is 0.17mm, which is equivalent to the nominal meniscus height of the capillaryseal at the axially opposite end of the motor when the motor is at restand stationary. The nominal total air volume of the slot portions 332 is1.19 mm³. This also represents the space available for axial jog. Thenominal pumping pressure at a junction of the slot portion 332 and therecirculation passageway 306 is 1.4 psi at 10 krpm. Other values may bedesigned within the pumping capillary sealing system, and arecontemplated by the teachings herein.

FIG. 8 illustrates another embodiment of an enlarged perspective view ofa pumping capillary seal in the form of a retainer 510, as in FIG. 3,and further comprising sweeping ribs 552A-552C, and a plenum region 554,in accordance with an embodiment of the present invention. The sweepingribs 552A-552C and plenum region 554 are situated on a radiallyextending surface. The sweeping rib 552A extends to an auxiliary pumpingrib 538 situated on an axially extending surface. Similarly, sweepingribs 552B and 552C extend to other auxiliary pumping ribs situated onthe axially extending surface. The sweeping ribs 552A-552C are situatedfor sweeping fluid from the axially extending surface to the radiallyextending surface and toward the bearing. Further, in the example shown,three truncated ribs (532A, 532B, 532C) are situated between sweepingribs 552A and 552B. The three slots or grooves adjacent to the truncatedribs are thus in fluid communication with each other. The truncated ribsalso pump fluid toward the bearing, but extend a shorter radial distanceas compared to the sweeping ribs, so as to provide a plenum region 554situated at a radial end of the truncated ribs. In an embodiment, thisplenum region 554 communicates with a vent hole 550 to ensure all slotsare vented.

Fluid containment is provided within the slots adjacent to the sweepingribs and the truncated ribs when the motor is stationary. However,plenum region 554 provides an added and increased fluid containmentregion for rapid oil volume changes, for example due to jog or a shockevent. These slots also provide for air containment, which can be ventedfrom the motor by way of vent holes 550. The vent holes 550 are situatedwithin the plenum region. In an alternative embodiment without the ventholes 550, as the motor spins and the pumping capillary seal transfersfluid into fluid reservoir, the slots receive air from theircorresponding pumping groove.

FIG. 9 is an enlarged perspective view of a pumping capillary seal inthe form of a cup 610, as in FIG. 5, and further comprising sweepingribs 652A-652C, and a plenum region 654, in accordance with anembodiment of the present invention.

The sweeping ribs 652A-652C and plenum region 654 are situated on aradially extending surface. The sweeping rib 652C extends to anauxiliary pumping rib 638 situated on an axially extending surface.Similarly, sweeping ribs 652A and 652B extend to other auxiliary pumpingribs situated on the axially extending surface. The sweeping ribs652A-652C are situated for sweeping fluid from the axially extendingsurface to the radially extending surface and toward the bearing.Further, in the example shown, three truncated ribs (632A, 632B, 632C)are situated between sweeping ribs 652A and 652B. The truncated ribsalso pump fluid toward the bearing, but extend a shorter radial distanceas compared to the sweeping ribs, so as to provide a plenum region 654situated at a radial end of the truncated ribs. In an embodiment, thisplenum region 654 communicates with a vent hole 650 to ensure all slotsare vented.

Fluid containment is provided within the slots adjacent to the sweepingribs and the truncated ribs when the motor is stationary. However,plenum region 654 provides an added and increased fluid containmentregion for rapid oil volume changes, for example due to jog or a shockevent. These slots also provide for air containment, which can be ventedfrom the motor by way of vent holes 650. The vent holes 650 are situatedwithin the plenum region. In an alternative embodiment without the ventholes 650, as the motor spins and the pumping capillary seal transfersfluid into fluid reservoir, the slots receive air from theircorresponding pumping groove.

Referring to FIG. 10, a sectional side view of a portion of a fluiddynamic bearing motor having a conical component is shown, illustratinga pumping capillary sealing system 710, in accordance with anotherembodiment of the present invention. A bearing 714 is defined betweenconical component 707 and sleeve 704. An interconnection passageway 718is defined between the relatively rotatable shaft 702 and sleeve 704. Afluid pumping capillary sealing system 710 is positioned at at least oneend of the bearing, for sealing fluid within the motor. Fluid pumpingcapillary sealing system 710 can be positioned on a facing surface ofthe shield 708 or the conical component 707. In the example shown, theshield 708 and the conical component 707 are fixed to the sleeve 704. Afluid passageway 706 is formed through the conical component 707 and isin fluid communication with the bearing 718. As in the previous designsdescribed, the fluid pumping capillary sealing system 710 includes afluid pumping groove and a capillary seal. The fluid pumping groovecomprises a slot portion and a rib portion, wherein the slot portionincreasingly diverges. The pumping direction is illustrated as anexample. The capillary seal is positioned at the facing surfaces of theshield 708 and the conical component 707. The slot portion diverges atleast to an area to enable a capillary seal fluid meniscus 705,extending from the diverging slot, to shift.

Modifications and variations may be made to the disclosed embodimentswhile remaining within the spirit and scope of the invention. Theimplementations described above and other implementations are within thescope of the following claims.

1. An apparatus comprising: a shaft, wherein the shaft is stationary; arotatable component configured to rotate with respect to the shaft; afluid operable to flow between the shaft and the rotatable component; alimiter at a first axial end of the shaft; a cup at a second axial endof the shaft; and an axially extending grooved region between thelimiter and the rotatable component.
 2. The apparatus of claim 1,wherein the grooved region includes a first end and a second end, and awidth of a groove at the first end is different than a width at thesecond end.
 3. The apparatus of claim 1, wherein the grooved regionincreasingly diverges.
 4. The apparatus of claim 1 further comprising aradially extending grooved region between the limiter and the rotatablecomponent.
 5. The apparatus of claim 1, wherein the axially extendinggrooved region is formed on the limiter.
 6. The apparatus of claim 1further comprising a capillary seal between the cup and the rotatablecomponent.
 7. The apparatus of claim 1 wherein the rotatable componentincludes a sleeve and a hub.
 8. An apparatus comprising: an axiallyextending groove in a limiter; and a rotatable component configured torotate with respect to the limiter; wherein the axially extending grooveand the rotatable component are configured to pump a fluid from a firstaxial end of the rotatable component towards a second axial end of therotatable component.
 9. The apparatus of claim 8, wherein the grooveincludes a first end and a second end, and a width of the groove at thefirst end is different than a width at the second end.
 10. The apparatusof claim 8, wherein the groove increasingly diverges.
 11. The apparatusof claim 8 further comprising a radially extending groove in thelimiter.
 12. The apparatus of claim 8, further comprising a cuppositioned at the second axial end of the rotatable component.
 13. Theapparatus of claim 12 further comprising a capillary seal between thecup and the rotatable component.
 14. The apparatus of claim 8 whereinthe rotatable component includes a sleeve and a hub.
 15. An apparatuscomprising: an axially extending grooved region at a first axial end ofa stationary component; a cup at a second axial end of the stationarycomponent; a thrust bearing at the first axial end of the stationarycomponent, wherein the thrust bearing is between the axially extendinggrooved region and the cup; a rotatable component configured to rotatewith respect to the cup; and a capillary seal between the cup and therotatable component.
 16. The apparatus of claim 15, wherein the groovedregion includes a first end and a second end, and a width of a groove atthe first end is different than a width at the second end.
 17. Theapparatus of claim 15, wherein the grooved region increasingly diverges.18. The apparatus of claim 15 further comprising a radially extendinggrooved region at the first axial end of the stationary component. 19.The apparatus of claim 15, wherein the axially extending grooved regionis formed on a limiter.
 20. The apparatus of claim 15 wherein therotatable component includes a sleeve and a hub.